The invention relates to a spindle for a ball screw and a method for producing this spindle.
For example, ball screws are widely used in automotive technology, primarily as actuators, because they enable a low-loss conversion of a rotational motion into a linear motion and vice versa. Such a ball screw comprises essentially a spindle and a nut or sleeve surrounding this spindle coaxially, between which ball-shaped roller bodies are arranged. Producing these components that are required for a ball screw from a solid material by means of cutting methods is challenging and therefore cost-intensive.
From the prior art, different methods and constructions of ball screws are known that permit relatively simple and therefore economical production of these ball screws. From DE 100 28 968 A1, such a sleeve is known for a screw drive that is formed from a sheet-metal blank that is flat at the beginning and in which a threaded profile is formed on one side and that is ultimately bent into a longitudinally slotted, hollow cylindrical sleeve, such that the threaded profile forms an internal thread on the sleeve. Roller bodies of the screw drive roll on the internal thread of the sleeve and an external thread on a threaded spindle, wherein a rotational motion is converted into a translational motion. During the production process of the sleeve, however, a longitudinal slot is produced in the sleeve, which can be completely closed only by pressing the sleeve into a hole provided with a corresponding fit. One disadvantage is that the rolling bodies of the screw drive cannot roll without reactions in the area of this longitudinal slot.
From DE 10 2011 081 966 A1, a method for producing a threaded part as a composite part, a roller screw drive, a linear actuator, and an electromechanical brake booster with such a composite part are known. The threaded part is formed as a composite part consisting of a thread turn and a tubular support part, wherein the thread turn is produced by a shaping process.
The tubular support part is preferably produced by a molding process, for example, injection molding or die casting, and simultaneously connected during this process with the thread turn using a material-bonding or positive-locking fit. Preferably, the support part is produced by die casting from a metal or injection molding from a plastic. According to one embodiment presented in that document, the threaded part is formed by a spiral-shaped or helical, wound sheet-metal strip with a flat, rectangular cross section, wherein a flat, channel-like recess is pressed in the sheet-metal strip as a thread turn. The windings of the sheet-metal strip are connected to each other, for example, by spot welding, by axial welding seams, or by a helical welding seam along the abutting longitudinal edges of the sheet-metal strip to form the threaded part that is then connected to the plastic support part by an injection molding process. This is disadvantageous in that, among other things, at least one weld seam to be realized with high accuracy is required to be created that also has a large longitudinal extent.